From the Star Tribune (and the US Census):
The three places in the nation with the highest median household income are all in Virginia, according to census data released Tuesday, while those with the highest rates of poverty are in four American Indian reservations, all in South Dakota.
The Virginia counties of Fairfax and Loudoun and the city of Falls Church had the highest median income, the data said, which spans 2005 to 2009. Falls Church was the highest at $113,313, up by 17 percent from 2000. The lowest median income was in Owsley County, Ky., at $18,869.
Of the five counties with poverty rates higher than 39 percent, four contain or are in reservations in South Dakota. The fifth, Willacy County, Tex., is on the Gulf Coast.